Method and apparatus pertaining to optimizing a radiation-treatment leaf-sequence plan

ABSTRACT

Determine first information regarding physical-movement limitations pertaining to at least one multi-leaf collimator and also determine second information regarding movement of the treatment target with respect to the given patient. Then, while optimizing a radiation-treatment leaf-sequence plan, constrain individually-planned leaf positions as a function, at least in part, of the first information, the second information, and planned positions of adjacent leaves. By one approach, the first information can comprise information regarding a speed (such as a maximum speed) at which individual leaves of the multi-leaf collimator are able to move during a treatment session. By one approach, the second information can comprise information regarding a distance (such as a maximum distance) that one or more parts of the treatment target may possibly move as compared to a presumed position used during the optimizing of the radiation-treatment leaf-sequence plan.

RELATED APPLICATION(S)

This application is related to co-pending and co-owned U.S. patentapplication Ser. No. 12/837,123, entitled METHOD AND APPARATUSPERTAINING TO USE OF JAWS DURING RADIATION TREATMENT and filed Jul. 15,2010, which is incorporated by reference in its entirety herein.

This application is also related to co-pending and co-owned U.S. patentapplication Ser. No. 12/860,466, entitled APPARATUS AND METHODPERTAINING TO RADIATION-TREATMENT PLANNING OPTIMIZATION and filed Aug.20, 2010, which is incorporated by reference in its entirety herein.

TECHNICAL FIELD

This invention relates generally to the optimization ofradiation-treatment leaf-sequence plans and more particularly to theoptimization of such plans.

BACKGROUND

The use of radiation to treat medical conditions comprises a known areaof prior-art endeavor. For example, radiation therapy comprises animportant component of many treatment plans for reducing or eliminatingunwanted tumors. Unfortunately, applied radiation does not discriminatebetween unwanted materials and adjacent tissues, organs, or the likethat are desired or even critical to continued survival of the patient.As a result, radiation is ordinarily applied in a carefully administeredmanner to at least attempt to restrict the radiation to a given targetvolume.

Collimators are often used to restrict and form the radiation-therapybeam. Some collimators have an aperture that can be adjusted in one ormore dimension. Adjustable apertures permit, to at least some degree,customization of the radiation-therapy beam's cross section to therebyattempt to better match the requirements of a given target volume.Multi-leaf collimators are an example of such a component. Multi-leafcollimators are comprised of a plurality of individual parts (known as“leaves”) that are formed of a high atomic numbered material (such astungsten) that can move independently in and out of the path of theradiation-therapy beam in order to selectively block (and hence shape)the beam.

Many treatment plans provide for exposing the target volume to radiationfrom a number of different directions. Arc therapy, for example,comprises one such approach. In such a case it often becomes useful ornecessary to adjust the multi-leaf collimator to accommodate variousdifferences that occur or accrue when moving the radiation source withrespect to the target volume. A radiation-treatment leaf-sequence planprovides information regarding useful or necessary adjustments to themulti-leaf collimator(s) at numerous sequential positions during such atreatment.

Optimizing such a plan can prove challenging. Amongst other things, theradiation target may not be located, shaped, or sized at the time ofadministering a treatment dosing as was thought to be the case whenforming and optimizing the radiation-treatment leaf-sequence plan. Toaccommodate such a circumstance it is known to plan for dynamicmodifications to a given radiation-treatment leaf-sequence plan tothereby attempt to adapt to a patient's presentation at the time ofadministering the corresponding treatment.

Though helpful to an extent, such a practice sometimes gives rise to oneor more new problems. As one example in these regards, a particularplanned or theoretically-available modification with respect to thestipulated position of one or more leaves of a multi-leaf collimator maybe impossible to achieve due to one or more corresponding physicallimitations. For example, a given leaf may simply not have enough timeto reach a modified position before the treatment process must continue.This, in turn, can render a planned or accommodated modificationtheoretically interesting but practically unhelpful.

BRIEF DESCRIPTION OF THE DRAWINGS

The above needs are at least partially met through provision of themethod and apparatus pertaining to optimizing a radiation-treatmentleaf-sequence plan described in the following detailed description,particularly when studied in conjunction with the drawings, wherein:

FIG. 1 comprises a front-elevational view as configured in accordancewith prior art practice;

FIG. 2 comprises a front-elevational detail view as configured inaccordance with prior art practice;

FIG. 3 comprises a front-elevational detail view as configured inaccordance with prior art practice;

FIG. 4 comprises a flow diagram as configured in accordance with variousembodiments of the invention;

FIG. 5 comprises a front-elevational view as configured in accordancewith various embodiments of the invention;

FIG. 6 comprises a front-elevational view as configured in accordancewith various embodiments of the invention; and

FIG. 7 comprises a block diagram as configured in accordance withvarious embodiments of the invention.

Elements in the figures are illustrated for simplicity and clarity andhave not necessarily been drawn to scale. For example, the dimensionsand/or relative positioning of some of the elements in the figures maybe exaggerated relative to other elements to help to improveunderstanding of various embodiments of the present invention. Also,common but well-understood elements that are useful or necessary in acommercially feasible embodiment are often not depicted in order tofacilitate a less obstructed view of these various embodiments of thepresent invention. Certain actions and/or steps may be described ordepicted in a particular order of occurrence while those skilled in theart will understand that such specificity with respect to sequence isnot actually required. The terms and expressions used herein have theordinary technical meaning as is accorded to such terms and expressionsby persons skilled in the technical field as set forth above exceptwhere different specific meanings have otherwise been set forth herein.

DETAILED DESCRIPTION

Generally speaking, these various embodiments facilitate optimizing aradiation-treatment leaf-sequence plan for use when treating a treatmenttarget in a given patient. This can comprise determining firstinformation regarding physical-movement limitations pertaining to atleast one multi-leaf collimator and also determining second informationregarding movement of the treatment target with respect to the givenpatient. These teachings then further provide for, while optimizing theradiation-treatment leaf-sequence plan, constrainingindividually-planned leaf positions as a function, at least in part, ofthe first information, the second information, and planned positions ofadjacent leaves.

By one approach, the aforementioned first information can compriseinformation regarding a speed (such as a maximum speed) at whichindividual leaves of the multi-leaf collimator are able to move during atreatment session. By one approach, the aforementioned secondinformation can comprise information regarding a distance (such as amaximum distance) that one or more parts of the treatment target maypossibly move as compared to a presumed position used during theoptimizing of the radiation-treatment leaf-sequence plan.

So configured, these teachings can serve to constrainindividually-planned leaf positions as a function, at least in part, ofplanned positions of adjacent leaves. In particular, this can compriselimiting a planned position of a given leaf such that the given leaf isat least likely to be physically capable of being moved, during atreatment session, to a new position that is similar to a position thatwas planned for another leaf that is adjacent to the given leaf.

By use of these teachings, then, a given radiation-treatmentleaf-sequence plan can be modified at a time of need and themodification will, in fact, be physically plausible and hence morelikely to preserve the efficacious value of the treatment. Inparticular, the leaves of the multi-leaf collimator will be able to moveto the modified positions as the modifications will be within a range ofmovement that the leaves can achieve. This, in turn, will help to assurethat movements of the treatment target are dutifully and suitablytracked to thereby help to ensure the planned beneficial results of thetreatment plan.

These teachings are readily employed in conjunction with existingequipment and hence can serve to greatly leverage the extended viabilityand useful lifetime of such equipment. These teachings are also highlyscalable and can be used with any number of multi-leaf collimators andwith any number leaves. In many cases these benefits can be achieved ina highly cost-effective manner.

These and other benefits may become clearer upon making a thoroughreview and study of the following detailed description. To begin, it maybe helpful to first briefly characterize certain aspects of the priorart.

FIG. 1 presents an illustrative example of a multi-leaf collimator 100having a plurality of leaves 101. As shown, each row of the collimatorhas two such leaves 101 that can be positioned horizontally (in thisexample, with other possibilities existing in these regards) along therow as desired. More particularly, an opening 102 can be formed byleaving a space between such leaves 101. For the sake of example themulti-leaf collimator 100 in this illustration has a plurality of suchopenings 102. These openings 102, in turn, comprise apertures throughwhich radiation can pass to reach the intended treatment target (notshown).

During a dynamic treatment process, such as an arc therapy treatmentprocess, the relative positions of these leaves 101 will typicallychange to accommodate variations in the presentation of the treatmenttarget. As noted above, however, sometimes the treatment target hasmoved (or has changed in shape or size) as compared to a presumedposition that a planning process employed when developing theradiation-treatment leaf-sequence plan. As a very simple example,presume here that the treatment target has moved a few millimetersdownwardly. To accommodate this shift in position it would be useful tosimilarly shift the collimator's aperture(s) 102 downwardly by a similaramount. Unfortunately, one or more physical limitations as tend tocharacterize a typical multi-leaf collimator can render this difficultor even impossible in some cases.

To exemplify this point in more detail, consider the leaves 101 shown inFIGS. 2 and 3. As noted above, these leaves 101 (denoted here as “A,”“B,” and so forth) are able to selectively move back and forth. Theseleaves 101, however, cannot move faster than some maximum speed. In atypical application setting there is also no more than a given amount oftime during which such leaves 101 can move before the process must carryon. This combination of limited time and maximum speed means that eachleaf 101 can move no more than a maximum distance 201 in either of itsdirections of motion.

As a result, when there is a need to move a given opening in a givendirection 202 (to accommodate, for example, corresponding movement ofthe treatment target), FIG. 3 represents the maximum change that theseleaves 101 can accommodate to try and accomplish the downward shiftingof the corresponding aperture. As is also illustrated in FIG. 3, thiswould result in a horizontal deficiency represented by 301. In sum andsubstance, the originally-shaped and positioned aperture is nowinappropriately located (and also possibly misshapen) because of a needto attempt to match, more or less in real time, movement or otherphysical changes regarding the treatment target.

Referring now to FIG. 4, an illustrative process 400 that is compatiblewith many of these teachings will now be presented. This process 400 canbe carried out by a control circuit of choice such as a digitalprocessor. The latter may comprise a dedicated platform or may comprisea more generally-programmable platform as desired. In many cases thisdigital processor can comprise a radiation-treatment leaf-sequenceplanner (as are known in the art) that has been configured to carry outthese teachings.

At step 401 this process 400 determines first information regardingphysical-movement limitations pertaining to at least one multi-leafcollimator. (In many application settings there will only be a singlemulti-leaf collimator. Where the application setting makes use of morethan one multi-leaf collimator, however, these teachings will readilyaccommodate determining this first information for some, or each, ofthis plurality of multi-leaf collimators.)

This first information can comprise, for example and at least in part,information regarding a speed (such as a maximum or average speed) atwhich individual leaves of the multi-leaf collimator are able to moveduring a treatment session. This first information can also comprise, inlieu of the foregoing or in combination therewith, an amount of timethat is available for the multi-leaf collimator leaves to move from abeginning position to a concluding position during a treatment session.As yet another example, this first information can comprise a maximumdistance that the multi-leaf collimator's leaves are able to move duringa treatment session from a beginning position to a concluding position.

These teachings will accommodate determining such information in anautomated manner. These teachings will also permit, however, suchinformation to be determined by accessing, for example, a memory havingsuch information already stored therein. In the latter case, forexample, an authorized person might have empirically determined thedesired information and entered the corresponding value(s) into such amemory.

At step 402 this process 400 also determines second informationregarding movement of the treatment target with respect to the givenpatient. This second information can comprise, for example, a distance(such as a maximum distance) that at least a part of the treatmenttarget may possibly move as compared to a presumed position used duringthe optimizing of the radiation-treatment leaf-sequence plan. As oneillustrative example in these regards, this second information mightcomprise the information that the treatment target, comprising a tumor,may shrink and may therefore be smaller by up to ten percent than acurrently anticipated size. As another illustrative example in theseregards, this second information might comprise the information that thetreatment target may be lower in the patient's body than expected by upto no more than 3 millimeters.

It is also possible, in combination with the foregoing or in lieuthereof, for this second information to comprise speed information.Illustrative examples in this regard can include, but are certainly notlimited to:

That a maximum movement speed of the target is some specified value,such as, for example, 4 mm/s;

That a maximum target movement speed has some specified relationship toanother parameter (for example, that the maximum target movement speedis one-half the maximum speed of the collimator leaves);

That a maximum target movement speed is defined as a number rangingfrom, for example, 0 to 10, where 0 represents a lack of movement and 10is a fastest anticipated (or possible) movement (Such a parameter neednot be tightly bound to a particular physical speed of the target, butcould, if desired, be a value that can be used to control the strengthof tracking constraint. Such a user definable parameter could pertain toan arbitrary scale with a corresponding constraining level beingexperimentally determined.).

Step 403 of this process 400 occurs, at least in part, while optimizinga radiation-treatment leaf-sequence plan for a given treatment target aspertains to a given patient. (Radiation-treatment plans are oftencalculated using an iterative process. Beginning with some initial setof settings, a radiation-treatment planning apparatus iterativelyadjusts one or more of those settings and assesses the relative worth ofthe adjusted plan. An iterative approach such as this is often referredto as “optimizing” the plan (where “optimizing” should not be confusedwith the idea of identifying an objectively “optimum” plan that issuperior to all other possible plans). Various approaches tooptimization are known in the art. As optimization in general comprisesa well-understood area of endeavor, and as these teachings are notoverly sensitive to particular selections in these regards, furtherelaboration will not be provided here regarding optimization techniquesand methodologies.)

More particularly, step 403 provides for constrainingindividually-planned leaf positions as a function, at least in part, ofthe aforementioned first information and second information as well asplanned positions of adjacent leaves. This can comprise, for example,limiting a planned position of a given leaf such that the given leaf isat least likely to be physically capable of being moved, during atreatment session, to a new position that is similar to a position thatwas planned for another leaf that is adjacent to the given leaf in orderto track movement of the treatment target. (As used herein, thisreference to being “physically capable of being moved” refers to theordinary, every-day leaf-movement performance of a given multi-leafcollimator and its corresponding motive and controlling components anddoes not include extraordinary measures one could theoretically practiceto improve such performance.)

This consideration of “adjacent” leaves can be limited to only leavesthat are immediately adjacent to the given leaf if desired. Someapplication settings may benefit, however, if this notion of beingadjacent is extended to include, for example, leaves that are within twoor three leaves of the given leaf (or some other range of choice).

Generally speaking, this step 403 can further comprise limiting plannedleaf positions such that the given leaves are at least likely to bephysically capable of being moved, during a treatment session and inreal time, to a new position that is similar to a position that wasplanned for another leaf that is adjacent to the leaf in question.

So configured, a sequence of leaf positions can be determined that arenot only suitable to achieve the intent of a given radiation treatmentplan but that can more likely adapt to physical changes with respect tothe location/shape/movement of the treatment target in a way thatpreserves that efficacious intent.

The extent to which such concerns for adjacent leaf positions influencesthe planned position for a given leaf can be varied as desired. That isto say, such a concern can be made weaker or stronger as may beappropriate to the needs or opportunities that tend to characterize agiven application setting. Absolute requirements in these regards, forexample, cannot likely be met with precision for all leaves in aone-hundred leaf collimator for each and every aperture configuration ina sequence of multi-leaf collimator settings. The need to comply withsuch a criterion can be made partially or wholly subservient to otherconsiderations as desired.

By way of some illustration in these regards, FIG. 5 provides a view ofa particular multi-leaf collimator configuration that complies with aweaker tracking constraint in these regards. FIG. 6, in turn, provides aview of a particular multi-leaf collimator configuration that compliesinstead with a stronger tracking constraint in these regards. Generallyspeaking, the stronger the tracking constraint, the more likely it willbe that the collimator apertures are rounder in shape. Such a tendencyis clearly apparent when comparing the somewhat rounder apertures ofFIG. 5 (which exemplifies a weak tracking constraint) with the aperturesof FIG. 1 (which reflects no tracking constraints whatsoever in theseregards) and the even-more rounded apertures of FIG. 6 (whichexemplifies a stronger tracking constraint).

The above-described processes are readily enabled using any of a widevariety of available and/or readily configured platforms, includingpartially or wholly programmable platforms as are known in the art ordedicated purpose platforms as may be desired for some applications.Referring now to FIG. 7, an illustrative approach to such a platform 700will now be provided.

This implementation platform 700 can comprise a control circuit 701 thatoperably couples to one or more memories. Such a control circuit 701 cancomprise a fixed-purpose hard-wired platform or can comprise a partiallyor wholly programmable platform. All of these architectural options arewell known and understood in the art and require no further descriptionhere.

By one approach, this control circuit 701 can operably couple to a firstmemory 702 that contains the aforementioned first information.Similarly, this control circuit 701 can operably couple to a secondmemory 703 that stores the aforementioned second information. Thesememories 702 and 703 can of course comprise a single component or can befurther parsed over a greater number of digital storage components asdesired. These memories 702 and 703 can also be located proximal to thecontrol circuit 701 (by sharing, for example, a same housing, rack, orfacility) or can be located remotely from the control circuit 701 (bybeing located, for example, in another facility, municipality, state,country, or the like).

As noted above, the control circuit 701 may comprise a partially orwholly programmable platform (such as a computer). In such a case,further memory 704 can operably couple thereto (or be a part thereof)and can store the instructions that, when executed by the controlcircuit, cause the control circuit to carry out one or more of thesteps, actions, or functions described herein.

Such an apparatus 700 may be comprised of a plurality of physicallydistinct elements as is suggested by the illustration shown in FIG. 7.It is also possible, however, to view this illustration as comprising alogical view, in which case one or more of these elements can be enabledand realized via a shared platform.

So configured, one can achieve reliable tracking of a treatment targetwith respect to the radiation dosing of that target. In particular,these teachings can improve the likelihood that the efficacious andintended benefits of a given radiation-treatment plan that employs oneor more multi-leaf collimators will in fact be achieved notwithstandingdifferences at the time of treatment with respect to the placement,shape, or size of the treatment target as compared to presumptions thatwere made in these regards at the time of optimizing thatradiation-treatment plan.

These teachings are readily employed in conjunction with most if not alloptimization approaches practiced today and will no doubt readilyaccommodate future approaches in these regards as well. Though readilypracticed and highly flexible in application, these teachings are alsonevertheless economically applied.

Those skilled in the art will recognize that a wide variety ofmodifications, alterations, and combinations can be made with respect tothe above described embodiments without departing from the spirit andscope of the invention, and that such modifications, alterations, andcombinations are to be viewed as being within the ambit of the inventiveconcept.

1. A method to facilitate optimizing a radiation-treatment leaf-sequenceplan for use when treating a treatment target in a given patient,comprising: at a digital processor: determining first informationregarding physical-movement limitations pertaining to at least onemulti-leaf collimator; determining second information regarding movementof the treatment target with respect to the given patient; whileoptimizing the radiation-treatment leaf-sequence plan, constrainingindividually-planned leaf positions as a function, at least in part, of:the first information; the second information; planned positions ofadjacent leaves.
 2. The method of claim 1 wherein the first informationcomprises, at least in part, information regarding a speed at whichindividual leaves of the multi-leaf collimator are able to move during atreatment session.
 3. The method of claim 2 wherein the speed comprisesa maximum speed at which the individual leaves are able to move duringthe treatment session.
 4. The method of claim 1 wherein the secondinformation comprises, at least in part, information regarding adistance that at least a part of the treatment target may possibly moveas compared to a presumed position used during the optimizing of theradiation-treatment leaf-sequence plan.
 5. The method of claim 4 whereinthe second information comprises, at least in part, informationregarding a maximum distance that the part of the treatment target maypossibly move during a treatment session as compared to the presumedposition.
 6. The method of claim 1 wherein the second informationcomprises, at least in part, information regarding a direction ofmovement as pertains to possible movement of at least a part of thetreatment target.
 7. The method of claim 1 wherein constrainingindividually-planned leaf positions as a function, at least in part, ofplanned positions of adjacent leaves comprises, at least in part,limiting a planned position of a given leaf such that the given leaf isat least likely to be physically capable of being moved, during atreatment session, to a new position that is similar to a position thatwas planned for another leaf that is adjacent to the given leaf in orderto track movement of the treatment target.
 8. The method of claim 7wherein limiting a planned position of a given leaf such that the givenleaf is at least likely to be physically capable of being moved, duringa treatment session, to a new position that is similar to a positionthat was planned for another leaf that is adjacent to the given leafcomprises limiting a planned position of a given leaf such that thegiven leaf is at least likely to be physically capable of being moved,during a treatment session, to a new position that is similar to aposition that was planned for another leaf that is directly adjacent tothe given leaf.
 9. The method of claim 7 wherein limiting a plannedposition of a given leaf such that the given leaf is at least likely tobe physically capable of being moved, during a treatment session, to anew position that is similar to a position that was planned for anotherleaf that is adjacent to the given leaf comprises limiting a plannedposition of a given leaf such that the given leaf is at least likely tobe physically capable of being moved, during a treatment session and inreal time, to a new position that is similar to a position that wasplanned for another leaf that is adjacent to the given leaf.
 10. Anapparatus to facilitate optimizing a radiation-treatment leaf-sequenceplan for use when treating a treatment target in a given patient,comprising: a first memory having first information stored thereinregarding physical-movement limitations pertaining to at least onemulti-leaf collimator; a second memory having second information storedtherein regarding movement of the treatment target with respect to thegiven patient; a control circuit operably coupled to the first memoryand the second memory and configured to, while optimizing theradiation-treatment leaf-sequence plan, constrain individually-plannedleaf positions as a function, at least in part, of: the firstinformation; the second information; planned positions of adjacentleaves.
 11. The apparatus of claim 10 wherein the first informationcomprises, at least in part, information regarding a speed at whichindividual leaves of the multi-leaf collimator are able to move during atreatment session.
 12. The apparatus of claim 11 wherein the speedcomprises a maximum speed at which the individual leaves are able tomove during the treatment session.
 13. The apparatus of claim 10 whereinthe second information comprises, at least in part, informationregarding a distance that at least a part of the treatment target maypossibly move as compared to a presumed position used during theoptimizing of the radiation-treatment leaf-sequence plan.
 14. Theapparatus of claim 13 wherein the second information comprises, at leastin part, information regarding a maximum distance that the part of thetreatment target may possibly move during a treatment session ascompared to the presumed position.
 15. The apparatus of claim 10 whereinthe second information comprises, at least in part, informationregarding a direction of movement as pertains to possible movement of atleast a part of the treatment target.
 16. The apparatus of claim 10wherein the control circuit is configured to constrainindividually-planned leaf positions as a function, at least in part, ofplanned positions of adjacent leaves by, at least in part, limiting aplanned position of a given leaf such that the given leaf is at leastlikely to be physically capable of being moved, during a treatmentsession, to a new position that is similar to a position that wasplanned for another leaf that is adjacent to the given leaf in order totrack movement of the treatment target.
 17. The apparatus of claim 16wherein the control circuit is configured to limit a planned position ofa given leaf such that the given leaf is at least likely to bephysically capable of being moved, during a treatment session, to a newposition that is similar to a position that was planned for another leafthat is adjacent to the given leaf by limiting a planned position of agiven leaf such that the given leaf is at least likely to be physicallycapable of being moved, during a treatment session, to a new positionthat is similar to a position that was planned for another leaf that isdirectly adjacent to the given leaf.
 18. The apparatus of claim 16wherein the control circuit is configured to limit a planned position ofa given leaf such that the given leaf is at least likely to bephysically capable of being moved, during a treatment session, to a newposition that is similar to a position that was planned for another leafthat is adjacent to the given leaf by limiting a planned position of agiven leaf such that the given leaf is at least likely to be physicallycapable of being moved, during a treatment session and in real time, toa new position that is similar to a position that was planned foranother leaf that is adjacent to the given leaf.
 19. A tangible memorycomponent having instructions stored therein, which instructions, whenexecuted by a computer, facilitate optimizing a radiation-treatmentleaf-sequence plan for use when treating a treatment target in a givenpatient by: determining first information regarding physical-movementlimitations pertaining to at least one multi-leaf collimator;determining second information regarding movement of the treatmenttarget with respect to the given patient; while optimizing theradiation-treatment leaf-sequence plan, constrainingindividually-planned leaf positions as a function, at least in part, of:the first information; the second information; planned positions ofadjacent leaves.